Main Entry: coun·ter·vail

Pronunciation: \ˌkau̇n-tər-ˈvāl\

Function: verb

Etymology: Middle English countrevailen, from Anglo-French cuntrevaloir, from cuntre- counter- + valoir to be worth, from Latin valēre — more at wield

Date: 14th century

transitive verb 1 : to compensate for
2 archaic : equal, match
3 : to exert force against : counteractintransitive verb : to exert force against an opposing and often bad or harmful force or influence